The Contractor will prepare purified Ig from acid eluates of coated tumor cells; examine ascites, T lymphoma, mammary carcinoma, and carcinogen-induced sarcoma cells for complement-dependent cytotoxicity, lymphocyte-mediated cytotoxicity, and antibody-mediated cytotoxicity, using uncoated tumor cells mixed with the acid eluates, in vivo coated tumor cells, and uncoated tumor cells as model systems; utilize mice immunized with noncross-reactive antigens and then challenged with ascites tumor cells and examine whether these cells show the capacity to bind the radiolabeled immunizing antigens and its effect on cytotoxicity assays; and study the surface binding capacity of cultured tumor cells for various immunoglobulin fractions obtained from normal mice or from plasmacytoma bearing mice.